Landfall probably does effect it, but more people know Oblivion than the Infernal City.
im not sure what ur getting at exactly, but...i think ur meaning to say that more game players know about oblivion than landfall. in that case, ur making the book and the loveletter (/and some other obscure lore tidbits) non-cannon. because that means theyre tailoring to mainstream kids who played oblivion on x-box and thot the horses looked cool, then somehow decided to make skyrim later on AFTER the book, but yet they made the events thats happened in the book not really happen because....??? the entire provience of skyrim would most-likely be killed off by the throat of the world asploding. lol so idk, i think it'll be after oblivion, but before the book.
it also makes no sense that there WOUDLNT be a dragon brake, because akatosh being positioned into a mortal avatar and then breaking free, in all sense of origonal tes lore, would make time bend like a hot noodle. but who knows, i dont hold my hopes up too too high from bethesda anymore anyway. like OMG A DRAGON IS GONNA END THE WORLD. lol, no. akatosh doesnt exactly do that, tho the JYLS and some big, hungry aether unstar farters sure have that agenda in mind.